Our laboratory will be involved in several aspects of lens research. We intend to delineate, more exactly than heretofore, seasonal variations in mitosis in the lens epithelium of amphibians. This will be done with animals we are maintaining in the natural state throughout the year. Past work shows the variation may be due to hypothalamus mediated influences which bring about release of pituitary factors. One of these is TSH - we would like to identify the others and determine their mode of action. Lens epithelial tissue cultures will be utilized to help understnad events at the molecular level. Even in the absence of such an understanding we have been able to control the extent of division in the germinative zone of frog lens and have found radiation cataract in these animals depends on cell proliferation. We will try to characterize the relationship further in amphibia and we intend to make a start with mammalian tissue. Work is also commencing on cell division triggered as a result of chemical endophthalmitis. We hope to elucidate the role of acid proteins as possible regulators of mitoses. This is a choice system because it is one of the few in which in vivo rather than an in vitro approach is realistic. The effects of several toxic agents upon corneal tissue will also be evaluated.